In MBR processes, membrane fouling has always been a significant issue limiting the hydraulic performance of the process. Due to membrane fouling, throughput from the MBR often decreases and more membrane is often required to compensate for the throughput loss.
Recently, research results (Nagaoka et al, 1996, 1998; Lee et al., 2002) have shown that one of the main causes of membrane fouling is biopolymer, which includes polysaccharides and proteins secreted by biomass grown in the activated sludge of the MBR.
Consequently, methods of using cationic polymers that do not react with the negatively charged membranes in contact with the activated sludge were developed (Collins and Salmen, 2004; Collins et al., 2005). In this method, various polymers are directly added to the MBR activated sludge and react with the biopolymers. The resulting particles, which consist of biopolymers and synthetic cationic polymers, do not foul the membrane surface.
Though these methods have been successfully implemented in most MBRs it has been observed that some sludges, especially industrial sludges, did not always coagulate well when low molecular weight water soluble cationic polymers were used. Therefore, there is a need for a more efficacious way of coagulating industrial sludges.